1. Field of the Invention
The present invention relates to an optical disc player for playing a musical program having additional information recorded on an optical disc. More particularly, the invention relates to a method of displaying additional information of a musical program during its performance and a method of erasing a recorded musical program, suitable for a mini disc recording/reproducing apparatus (MD apparatus).
2. Related Background Art
There is known a mini disc (MD) which is one type of rewritable photomagnetic discs. A mini disc is formed with a pit information record area at the central area of the disc and a recordable area at the outer area. The recordable area includes a user's TOC (Table of Contents) area (U-TOC) and a program area. The recordable area has no pit, but a groove is engraved for the guidance to trucks  tracks. Information is recorded in the recordable area along the groove.
The groove sways like wobble. The rotation of the disc is controlled by a signal having an average frequency of 22.05 kHz and generated based on the wobble. Absolute times (address information) relative to the record start position are FM-modulated and recorded in the wobble.
Data record is achieved by magnetizing a magnetic film. Namely, the magnetic film is heated to a Curie point or higher by a laser spot while applying a magnetic field which reverses its polarity depending upon an input signal. The signal is therefore recorded in the magnetic film as a change in the magnetization direction. Such data record can be performed even on an already recorded area, i.e., data overwrite is possible.
The record position is managed by the information recorded in U-TOC. Recorded in the program area is information including a start time, end time, title, and the like for each truck  track number (TNO) which is a natural number beginning with “1” and assigned to each musical program. If TNO and its additional information is erased from U-TOC, the corresponding recordable area is handled as an unrecorded area.
When an MD disc is loaded on an optical disc player, U-TOC information recorded in the MD disc is read and copied to a RAM. Thereafter, data recording/reproducing is managed by the U-TOC information stored in RAM. Each time a musical program is recorded or erased, the contents of RAM are updated and recorded-in U-TOC before the disc is unloaded from the apparatus.
Additional information as well as the start time, end time, and the like of each musical program is also recorded in TOC area of a reproduction-only mini disc formed with pit trains over the whole area of its information record area.
Address information can be read from such a mini disc during the performance of a musical program. Therefore, it is possible to display a total time from the start address of TNO 1 to the address of TNO under the performance, on a display unit. The start time of TNO under the performance can also be known from TOC information, it is possible to display a single time from the start address of TOC under the performance to the current address, on the display unit. The additional information in TOC area includes a title of each TNO so that the title of each musical program under the performance can also be displayed.
Conventionally, in an optical disc player such as a CD player, a selective display between a total time, a single time, and the like has been realized by designating a display mode. Such a selective display has been used because the screen of a display unit is too small to display all information on it and characters displayed become too small.
While playing an optical disc recorded with address information and additional information such as the title of each TNO, if a mode of selectively displaying a title is set, the lapse time is not displayed. In such a case, a user accustomed with a screen display of a conventional optical disc player such as a CD player feels something restless. In addition, it is not convenient for the user to be unable to know the remaining time of the musical program under the performance.
In erasing a musical program recorded in such a mini disc, TNO of the program is keyed in to display it on a display screen and an erase key is depressed to delete TNO information from U-TOC area. This method is unsatisfactory, however, in that if a user keys in a different TNO inadvertently, the musical program not intended to be erased, is deleted.